(ChemotherapyAdvisor) – Chemotherapeutic effects seem to increase with tumor size, according to a multinational team of researchers. This conclusion is based on a paper entitled “A Pooled Exploratory Analysis of the Effect of Tumor Size and KRAS Mutations on Survival Benefit From Adjuvant Platinum-Based Chemotherapy in Node-Negative Non–Small Cell Lung Cancer,” which will be published in the June issue of the Journal of Thoracic Oncology, but is currently available online.

The investigators aimed to explore the prognostic and predictive effects of the new tumor size (T-size) descriptors and KRAS mutation status for staging node-negative non-small cell lung cancer, as published in the National Cancer Institute of Canada Clinical Trials Group JBR.10 trial and the Cancer and Leukemia Group B-9633 trial.

After pooling data from these two trials, the investigators re-classified tumors of 538 eligible patients. In this pool, 288 (53.5%) were T2a, 111 (21%) T2b, 62 (11.5%) T3, whereas 77 (14%) T≤3 cm were excluded. KRAS mutations were detected in 104 of 390 patients (27%). T-size was prognostic for disease-free survival (P=0.03), but borderline for overall survival (OS; P=0.10), on multivariable analysis. Significant interaction between the prognostic value of KRAS and tumor size was observed for OS (P=0.01), but not disease-free survival (P=0.10).

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There was a non-significant trend (P=0.24) for increased chemotherapy effect on OS with advancing T-size (hazard ratio [HR] T2a 0.90, [0.63–1.30]; T2b 0.69, [0.38–1.24]; and T3 0.57, [0.28–1.17]). The HR for chemotherapeutic effect on OS in T2a patients with KRAS wild-type tumors was 0.81 (P=0.36), whereas a trend for detrimental effect was observed in those with mutant tumors (HR 2.11; P=0.09; interaction P=0.05). Similar trends were observed in T2b to T3 patients with wild-type (HR 0.86; P=0.62), and KRAS mutant tumors (HR 1.16; P=0.74; interaction P=0.58).

The investigators concluded that “chemotherapeutic effects seem to increase with tumor size. However, this small study could not identify subgroups of patients who did or did not derive significant benefit from adjuvant chemotherapy based on T-size or KRAS status.”